Measuring device for determining the density, the mass flow and/or the viscosity of a gas-charged liquid, processing system having such a measuring device, and method for monitoring a gas-charged liquid

Abstract

A measuring device for determining the density, the mass flow and/or the viscosity of a gas-charged liquid includes an oscillator, having a media-conducting measuring tube and two vibrational modes having media-density-dependent natural frequencies; an exciter for exciting the two vibrational modes; a vibrational sensor for detecting vibrations of the oscillator; and an operating and evaluating circuit to apply an excitation signal to the exciter, detect signals of the vibration sensor, determine current values of the natural frequencies of the two vibrational modes of the oscillator and fluctuations of the natural frequencies. The operating and evaluating circuit is designed to determine a first media state value, wherein the operating and evaluating circuit is furthermore designed to determine a second media state value which represents a gas charge of the medium.

The invention claimed is: 
     
       1. A measuring device for determining the density, the mass flow, or the viscosity of a gas-charged liquid, comprising: at least one oscillator which has at least one vibratable measuring tube for conducting the medium, and which has at least two vibrational modes whose natural frequencies depend upon the average density of the gas-charged liquid and on the gas volume fraction of the gas-charged liquid; at least one exciter for exciting both vibrational modes; at least one vibrational sensor for detecting vibrations of the oscillator; and an operating and evaluating circuit configured to apply an excitation signal to the exciter, to detect signals of the vibrational sensor, to determine current values of the natural frequencies of both vibrational modes of the oscillator and fluctuations of at least one of the natural frequencies on the basis of the signals of the vibrational sensor, wherein the operating and evaluating circuit is further configured to determine a first media state value on the basis of the fluctuations, wherein the operating and evaluating circuit is further configured to determine, on the basis of the two natural frequencies, a second media state value which represents a gas charge of the medium, wherein the operating and evaluating circuit is further configured to output a media state message into which the first media state value and the second media state value are incorporated; wherein the first media state value identifies a presence of free gas bubbles in the medium; wherein the second media state identifies a gas charge with microbubbles; wherein the operating and evaluating circuit is configured to further determine the second media state value as a function of a pressure value which represents the media pressure in the measuring tube; wherein the media state message contains, in addition to the first media state value information about which flow regime of the first media state value was determined, wherein the information about the flow regime comprises a flow measured value or a value range of the flow measured value, wherein the flow measured value comprises a flow velocity, a mass flow rate, a volume flow rate or a Reynolds number; wherein the media stage message identifies a state of the medium with regard to gas charge based on the presence of free gas bubbles and the gas charge with microbubbles. 
     
     
       2. A measuring device for determining the density, the mass flow, or the viscosity of a gas-charged liquid, comprising:
 at least one oscillator which has at least one vibratable measuring tube for conducting the medium, and which has at least two vibrational modes whose natural frequencies depend upon the average density of the gas-charged liquid and on the gas volume fraction of the gas-charged liquid; 
 at least one exciter for exciting both vibrational modes; 
 at least one vibrational sensor for detecting vibrations of the oscillator; and 
 an operating and evaluating circuit configured to apply an excitation signal to the exciter, to detect signals of the vibrational sensor, to determine current values of the natural frequencies of both vibrational modes of the oscillator and fluctuations of at least one of the natural frequencies on the basis of the signals of the vibrational sensor, 
 wherein the operating and evaluating circuit is further configured to determine a first media state value on the basis of the fluctuations, 
 wherein the operating and evaluating circuit is further configured to determine, on the basis of the two natural frequencies, a second media state value which represents a gas charge of the medium, 
 wherein the operating and evaluating circuit is further configured to output a media state message into which the first media state value and the second media state value are incorporated; 
 wherein the first media state value identifies a presence of free gas bubbles in the medium; 
 wherein the second media state identifies a gas charge with microbubbles; 
 wherein the operating and evaluating circuit is configured to further determine the second media state value as a function of a pressure value which represents the media pressure in the measuring tube; 
 wherein the first media state value is normalized with a normalization function that is dependent upon the flow measured value; 
 wherein the media stage message identifies a state of the medium with regard to gas charge based on the presence of free gas bubbles and the gas charge with microbubbles. 
 
     
     
       3. The measuring device of  claim 1 , wherein the first media state value is a function of the fluctuations in the natural frequency, wherein the function furthermore exhibits a natural-frequency-dependent normalization. 
     
     
       4. The measuring device of  claim 1 , wherein the first media state value comprises a gas volume fraction of the medium in the form of free gas bubbles or a range of values for the gas volume fraction. 
     
     
       5. A processing system for processing a medium having a gas-charged liquid, wherein the processing system comprises:
 at least one pipeline for conducting the medium; 
 at least one measuring device according to  claim 1 , which is installed in the pipeline; 
 at least one actuator for influencing the medium; 
 a process control system which is connected to the measuring device and the actuator in order to receive the media state message and control the actuator, wherein the process control system comprises a data memory in which at least one target value is stored for the gas charge, wherein the process control system is configured to control the actuator as a function of the media state message in order to regulate the gas charge to the at least one target value. 
 
     
     
       6. The processing system of  claim 5  for processing a medium, wherein the actuator comprises a temperature control device, a pump, a valve, a ventilator, a stirring device, or a mixer. 
     
     
       7. A method for monitoring a gas-charged liquid with a measuring device, which has at least one oscillator with at least one measuring tube for conducting the gas-charged liquid, wherein the measuring device includes at least one oscillator which has at least one vibratable measuring tube for conducting the medium, and which has at least two vibrational modes whose natural frequencies depend upon the average density of the gas-charged liquid and on the gas volume fraction of the gas-charged liquid, at least one exciter for exciting both vibrational modes; at least one vibrational sensor for detecting vibrations of the oscillator; and an operating and evaluating circuit configured to apply an excitation signal to the exciter, to detect signals of the vibrational sensor, to determine current values of the natural frequencies of both vibrational modes of the oscillator and fluctuations of at least one of the natural frequencies on the basis of the signals of the vibrational sensor, wherein the operating and evaluating circuit is further configured to determine a first media state value on the basis of the fluctuations, wherein the operating and evaluating circuit is further configured to determine, on the basis of the two natural frequencies, a second media state value which represents a gas charge of the medium, wherein the operating and evaluating circuit is further configured to output a media state message into which the first media state value and the second media state value are incorporated, wherein the method comprises the following steps: determining natural frequencies of at least two bending vibrational modes; determining fluctuations of at least one of the natural frequencies; determining a first media state value based on the fluctuations in the natural frequency; determining a second media state value based on the two natural frequencies, which represent a gas charge of the medium; and outputting a media state message into which the first media state value and the second media state value are incorporated; wherein the first media state value identifies a presence of free gas bubbles in the medium; wherein the second media state identifies a gas charge with microbubbles: wherein the first media state value comprises a value dependent upon a fraction of free gas bubbles in the medium; wherein the second media state value depends upon a gas volume fraction in the form of micro-bubbles in the medium; wherein the second media state value indicates a gas volume fraction in the form of micro-bubbles in the medium; wherein the operating and evaluating circuit is configured to further determine the second media state value as a function of a pressure value which represents the media pressure in the measuring tube; wherein the media state message contains, in addition to the first media state value, information about which flow regime of the first media state value was determined, wherein the information about the flow regime comprises a flow measured value or a value range of the flow measured value, wherein the flow measured value comprises a flow velocity, a mass flow rate, a volume flow rate or a Reynolds number; wherein the media stage message identifies a state of the medium with regard to gas charge based on the presence of free gas bubbles and the gas charge with microbubbles. 
     
     
       8. The measuring device of  claim 2 , wherein the first media state value is a function of the fluctuations in the natural frequency, wherein the function furthermore exhibits a natural-frequency-dependent normalization. 
     
     
       9. The measuring device of  claim 2 , wherein the first media state value comprises a gas volume fraction of the medium in the form of free gas bubbles or a range of values for the gas volume fraction. 
     
     
       10. A processing system for processing a medium having a gas-charged liquid, wherein the processing system comprises:
 at least one pipeline for conducting the medium; 
 at least one measuring device according to  claim 2 , which is installed in the pipeline; 
 at least one actuator for influencing the medium; 
 a process control system which is connected to the measuring device and the actuator in order to receive the media state message and control the actuator, wherein the process control system comprises a data memory in which at least one target value is stored for the gas charge, wherein the process control system is configured to control the actuator as a function of the media state message in order to regulate the gas charge to the at least one target value. 
 
     
     
       11. A method for monitoring a gas-charged liquid with a measuring device, which has at least one oscillator with at least one measuring tube for conducting the gas-charged liquid,
 wherein the measuring device includes at least one oscillator which has at least one vibratable measuring tube for conducting the medium, and which has at least two vibrational modes whose natural frequencies depend upon the average density of the gas-charged liquid and on the gas volume fraction of the gas-charged liquid; 
 at least one exciter for exciting both vibrational modes; 
 at least one vibrational sensor for detecting vibrations of the oscillator; and 
 an operating and evaluating circuit configured to apply an excitation signal to the exciter, to detect signals of the vibrational sensor, to determine current values of the natural frequencies of both vibrational modes of the oscillator and fluctuations of at least one of the natural frequencies on the basis of the signals of the vibrational sensor, 
 wherein the operating and evaluating circuit is further configured to determine a first media state value on the basis of the fluctuations, 
 wherein the operating and evaluating circuit is further configured to determine, on the basis of the two natural frequencies, a second media state value which represents a gas charge of the medium, 
 wherein the operating and evaluating circuit is further configured to output a media state message into which the first media state value and the second media state value are incorporated, wherein the method comprises the following steps: 
 determining natural frequencies of at least two bending vibrational modes; 
 determining fluctuations of at least one of the natural frequencies; 
 determining a first media state value based on the fluctuations in the natural frequency; 
 determining a second media state value based on the two natural frequencies, which represent a gas charge of the medium; and 
 outputting a media state message into which the first media state value and the second media state value are incorporated; 
 wherein the first media state value identifies a presence of free gas bubbles in the medium; 
 wherein the second media state identifies a gas charge with microbubbles; 
 wherein the first media state value is normalized with a normalization function that is dependent upon the flow measured value; 
 wherein the media stage message identifies a state of the medium with regard to gas charge based on the presence of free gas bubbles and the gas charge with microbubbles.